The growth of silver on GaAs{001}: Epitaxial relationships, mode of growth and interfacial diffusion

Abstract

In this paper we report a detailed investigation of the epitaxial growth of silver films on GaAs{001} layers prepared in situ by molecular beam epitaxy. The epitaxial relationship between silver and GaAs{001} together with the mode of metal growth and the interfacial diffusion were mainly determined by low energy electron diffraction, Auger electron spectroscopy (AES) and scanning electron microscopy. The epitaxial relationship was shown to depend markedly on the growth temperature: below 200 °C it is Ag(011)//GaAs{001} while above 200 °C it is Ag(001)//GaAs{001} The temperature of growth also plays a key role in determining the mechanism of the metal growth. The very first stages of growth (submonolayer and monolayer range) were studied using the method of Auger signal-time plots: at low temperature (about 50 °C) the growth mechanism is very close to the two-dimensional layer-by-layer type (Franck-van der Merwe mode) while three-dimensional growth begins to appear when the temperature is raised and becomes completely dominant above 400 °C, where well-defined crystallites develop. AES results are well correlated with the topology of the metal films as revealed by scanning electron microscopy. AES was also used to probe interfacial diffusion: it was found that gallium out-diffusion through the metal layer becomes significant above 400 °C.